Scientists have learned how dangerous aerosols are formed
26.02.2021

Tomsk State University and University of Helsinki scientists have discovered new ways of forming air-polluting aerosols, which involve natural hydrocarbons released by conifers. The results of their quantum chemical calculations has been published in Nature Communications (Q1).

Rashid Valiev, an associate professor at the TSU Faculty of Physics, and colleagues from Finland explained the oxidation of terpene molecules in ozonolysis reactions. This made it possible to discover new ways of forming aerosols that negatively affect the climate and ecology of the environment. The source of terpenes, which have been studied by physicists, are coniferous forests.

- We carried out multireference quantum-chemical calculations and found that the previously known data on ozonolysis of terpene molecules were not entirely correct. Our calculations showed that the values of activation barriers for various reaction pathways differ significantly from those that were previously assumed, and the reactions themselves proceed in a more complex way, says Rashid Valiev. - Thus, using experimental and theoretical methods, we were able to correctly compare the different paths of the ozonolysis reaction and explain step by step the stages of the formation of the products of this reaction.

Terpenes are an important class of volatile organic compounds and, according to recent research, can be converted very quickly into aerosols with low volatility. However, it was possible to understand the mechanism of this transformation only after calculations by Valiev's scientific group, which showed that the excess energy from the initial ozonolysis reaction can lead to novel oxidation intermediates without steric strain, allowing the rapid formation of products with up to 8 oxygen atoms.

Terpenes are involved in the formation of so-called secondary aerosol particles, which are created mainly by the interaction of hydrocarbons with various oxidants. Such particles are very dangerous for humans and animals, as they penetrate deeply into the lungs. Also, they reflect the sun's rays in the infrared range and are therefore associated with climate problems. Therefore, the study of the mechanisms of formation of these particles is an important task for atmospheric chemistry and physics.

As Rashid Valiev added, pollution with aerosol particles leads to the deaths of 2.9 million people annually - an order of magnitude greater than those from armed conflicts. Primary aerosol particles such as dust dominate the total mass of atmospheric aerosol. But the vast majority of submicron aerosol particles that are responsible for most of the deaths from air pollution are in fact secondary.

The next step in the work of the international scientific team will be to explain the chemistry of iodine in the context of ozone.